1. Field of the Invention
Embodiments disclosed herein generally relate to methods of determining well disposal capacity. More specifically, embodiments disclosed herein generally relate to determining a maximum injection volume in a selected formation for a waste injection process.
2. Background Art
Waste Injection (WI) operation involves the collection and transportation of drilling waste from solids control equipment on a rig to a slurrification unit. The slurrification unit subsequently grinds the cuttings into small particles in the presence of a fluid to make a slurry. The slurry is then transferred to a slurry holding tank for conditioning. The conditioning process affects the rheology of the slurry, yielding a “conditioned slurry.” The conditioned slurry is then pumped into a disposal well or through a casing annulus into sub-surface fractures in the formation (commonly referred to as the disposal formation) under high pressure. The conditioned slurry may be injected intermittently in batches into the disposal formation. The batch process typically includes injections of similar volumes of conditioned slurry and then waiting for a period of time (e.g., shutting-in time) after each injection. Each batch injection may last from a few hours to several days or even longer, depending upon the batch volume and the injection rate.
Batch processing (i.e., injecting conditioned slurry into the disposal formation and then waiting for a period of time after the injection) allows the fracture to close and dissipate, to a certain extent, the build-up of pressure in the disposal formation. However, the pressure in the disposal formation typically increases due to the presence of the injected solids (i.e., the solids present in the drill cuttings slurry).
With large-scale WI operations, release of waste into the environment must be avoided and waste containment must be assured to satisfy stringent governmental regulations. Important containment factors considered during the course of the operations include: the location of the injected waste and the mechanisms for storage; the capacity of an injection well or annulus; whether injection should continue in the current zone or in a different zone; whether another disposal well should be drilled; and the required operating parameters necessary for proper waste containment.
Modeling of WI operations and prediction of disposed waste extent are used to address these containment factors and to ensure the safe and lawful containment of the disposed waste. Modeling and prediction of fracturing is also used to study WI operation impact on future drilling, such as the required well spacing, formation pressure increase, etc. A thorough understanding of the storage mechanisms in WI operations may also be important for predicting the possible extent of the injected conditioned slurry and for predicting the disposal capacity of an injection well.
Accordingly, there exists a need for a more accurate assessment or estimations of well disposal capacity.